Method of digesting nitrocellulose



y 1932- A. c. PRESTON ET AL 1,867,757

METHOD OF DIGESTING NITROCELLULOSE Original Filed July 13. 1928 REGULATIHB ALUE T AIR Srormcs FUMP/ RELIEF UALUE Ex PANsmM Z0 TANK lldl celluzose D l G E 5 TO K SUPPLY 5 Patented July 19, 1932 mm ems Amman. PRESTON, F WILBRAHAM, AND see s o; Gauss, on srninerrunn, Me s MAINE, A CORPORATION or MASSACHUSETTS v 'sAoE'UsE'rTs, Assie'non's 'ro VTHE FIBERLorn CORPORATION, or INDIAN onorrnnn,

1 E H D IG ESTING ,NI i- Original application filed July s, 1 28, Serial No. 292,555. 'mvia'aanauiis applicationifiled lliayb,

1929 Serial 'plish this according to one method it isconfined in a closed vat andaheated 'cooking liquid is circulatedtherethrough, as for instance,by a pump whichdischargestheliquid intojthe'lower side of the vat and has its tsuctionconnected to the upper side thereof. By this method the liquid circulates up through the material and uniformly, permeates the same and at the same time tends to prevent the material settling in the vat, provides uniform distribution ofheat throughout the-mass and carries dangerous gases of decomposition away. It hasbeen found thatin order to produce the best digesting results, it is most desirable to maintai'nfthe temperature-of the liquid at a considerable temperature somewhat above the boiling temperature, say 270 degrees Fah. and at a "pressure of approximately -pou'nds persquare at the suctionjside of the pump is less than that at the dischargeside thereof so that under the temperature and pressure conditions as statedthere is a tendency for the liquid to flash into steam.- The result of this flashing is that the desired circulating of the liquid is interrupted, the materialis not uniformly cooked, explosions are likely to occur in connection with the gases whichiare formed by the decomposition of the material, and being no longer carried upward positively to a vent,

may become localized at points inthe mass undergoing digestion,

ventionis the provision of a method for diten, To this end the benefits of a liighicook- 3 I The novel features of ipanying idrawingiin which :v a

scribed inidetailph 1 ing temperaturemaybe' taken of and at the zsa'me-tim'ethe dangers usually present when explosive gases are developed as withthe old-method referred to may be eliminated. r

v our inventlon are ac-, complished by means of a novel mode'of operation and apparatus to be hereinafter more fully described" in the form at present preferred and which forvillustrative purposes 7 may be taken in 7 connection with the The figure represents a digesting apparaaccomv tus and circulating pump therefor. with the v ,noveL features of our"lnvention associated therewith In order to facilitate a 'cleariunderstandratusLshown in the drawing will now bew'de- A supply pipeg 5 leading into one" branch :of a Y fitting 6'is providedwhich has a valve --7. 5 This pipe is arranged .for conducting 'nitro-cellulose' to an opening at the lowerend of the di gester D while a shut-ofiivalvei between the Y fittingfi anddigester is :provided.

The nitro-cellulose or other material to i be digested may be delivered to the pipeline 5 from any convenient location and allowed to flowby gravityor pumped under pressure to the digester as may be desired. It will'be understood that the "material is preferably conducted through the pipeby a liquid which maybe called acarrying liquid, which fliquid may be water or whatever-is desired or neces ing or digesting liquid, e I g 4 A screen-10 -preferably in the form-iota sary to carrythe liquid or to serve as a'cookperforated plateymetal cloth or the like,1 is

fixed to i a frame ll, which is suspended by chains-12 from hooks not-shown-at the upper end ofthe digester. Thisscreen may be sup- 7 ported-by thechainsso that its edges will Therefore the principal object of-this inabut the inner walls of the digester and when ingofthelmethod of the finventionthe appabeing digested from passing out through the outletl?) at the upperside of the digester.

, A pip'e connection 14, in communication with the outlet-13, isconneeted to a T fitting 1F, h e v l e- 1 and,16M th i ll tef loo" T fitting F are arranged so that liquid from. the digester may be directed either down-' reliefvalve 21, which valve may beef any well-known form adapted to 'openat some predetermined pressure and allow the escape of pressure from the digester.

A pipe 22 extending from the cover 3 is providedwith a shut-oil valve24 and is connected to the lower side of a closed-expansion tank 25. This tank is adapted to accommo- ;date .:the ordinary fluctuations of pressure within the system during the digesting operation and is connected by a pipe-26- to the -irelief valve pipeQO so that any excessive pressure will be released through .said relief valve. A pipe s'uchas shown, or other means, -may be provided oncontrol \by a valve to permit a predetermined; amount. of :pressure --and/or=gases to escape from tank,'25.-

A filling 'pipe-Q'Tcontrolled by. a valve 28 and leading. into; the upper side of "theexpansion tank is '..arranged for delivering water :orother-liquid to1the said tank 25.

1A steam ilinei'33, -.which maybe connected 30 to any suitable source ot supply,;isv arranged to conduct the same to the circulating pipe -18. iTheadmission ofrsteamito the pipe 18 is 7 preferably controlled by a: :shut; ofl valve .34 n I -a11d-= anthermostatically controlled. V3.1V8"35, 95 while a check valve 36 preventsor checks va "'flowzofzpressure from the pipe 18;to the .pipe 533:: and-steam system connected: thereto. A sdownwardlyzdirectedrpipe or tube 37'is pro- ;vided within: the v pipez 18. torzdirecting: the steam: trom I :the. iline .133 downwardly win: the .Jpipe; 18 :in the. direction :of :fiow of gfluid circulatingthroughgthe-system.

,lhe-valvei maybe of the electrically opaeratedv type in common-use and may be, actucated-uor controlled :by thermostatic elements 1:38: of ordinary; .fofrm 'located'ein the: T" fitting Theparticular form-of the valve35 and actuating. means therefor is not important f-'. f0rthe.practice of the invention, it .being in- -:tended: to indicate. :that :inthe. --operation of silica apparatus it is desirable and necessary to have the control of theadmissionof steam insthe digesteniand system. 7 The-pipe 18,- atzits lQWEIjGIldflSE connected tov a va-lvez ltl adjacent :the Y fitting 56-, and to :the inletaor suctionside 41 of apump. P. The wpumpP? may: be: of any desired 'vform, @cen- :trifugal: or otherwise,- and maybe operaiitivelyconnecteds to any power supplying *means such as a motorMshown.

A pipe 45 in communication withthe out- -l'etside; of'the pump P is connectedby means of -t-he' connection' ldto a pipej47 which :is connected to the-Yfitting 6 and-to a discharge riser 48. Valves 49 and 50 of the pipes 47 and 48 are provided so that the material delivered or discharged by the pump may be directed either to the digester-2 or the discharge line 48. v

Nozzles or jets extending through the lower end of the digester are connected to a pipe '56 surrounding thedigester and a supply "pipe '57 leading thereto-which may be connected to any suitable water or-fluid'supplying system.v A valve 58 of the pipe 57 will control the flow of fluid to the jets for the purpose to; be described.

In the-operation of the apparatus thus described the valves 15, 7, 28, 40 and 50 are closed so that the carrying liquid is'cii'culat "ed .up throughthe vat and nitrocellulose by the pump and back againto thepump.

In the operation-.ofzthe apparatus, at relatively low pressures and temperatures, -a-

slight relative difference in pressure'between the-suction and dischargesides ofzthe pump is not likely to produce the'undesirable efiects referred to. When operating however atrela- :tively high temperatures or above the boiling point as is desirablefor best'results ithe flashing ordinarily occurs. To obviate this condition we provide means for adding pressure to the system so as to compensate for any-drop in pressure referred towhich brings -about the undesirable results. This maybe accomplished in one way by means of an. air pump 60 which'is connected to a storage tank -62 that isin turn connected-by :suitablepip- :ing 64 to the expansion chamber25 as shown. A regulating valve of any-well known form out departing from the scope ofthe invention and we prefer therefore to be limited, if at all, bythe appended claims rather than-by the fore oin descri tion. iundercontrol of the temperature-prevailing D b p "What we claim is 1. The method of digesting nitro-cellulose which consists in, confining the nitrocellulose in a closed system, circulating a' digesting liquid there'through, heating said liquid and in admitting air pressure to said system to bring the pressure therein above that at which the said liquid will flash into steam.

'2. The method of digesting nitrocellulose which consists in, confining said nitrocellulose in a closed system, subjecting the material to the action of a'digesting liquid, heating said liquid venting thesystem to allow the escape of explosive gases and in imposing pressure on the digesting liquid in said system to compensate for the escape of gases and prevent the flashing of the liquid into steam.

3. The method of digesting nitro-cellulose which consists in, confining said material in a closed system, circulating digesting liquid through said system and heating said liquid above its boiling point and in imposing air in said liquid from a source outside said system at a pressure which will bring the pressure in a said system above that at will flash into steam.

4. The method of digesting nitro-cellulose which consists in, confining nitro-cellulose in a part of a closed system, circulating a digesting liquid through the said nitro-cellulose and the said system, heating said liquid and in admitting air pressure to said system to bring the pressure therein above that at which the said liquid will flash into steam.

which said liquid In testimony whereof we afiix our signa tures.

ARTHUR G. PRESTON. GEORGE G. GRESS. 

